This invention relates to a process for the production of phenol and thiophenol compounds. Such compounds are well-known, phenols as solvents and intermediates and thiophenols as anti-oxidants, polymerization inhibitors, intermediates, etc.
Various processes for preparing thiophenols have previously been described. For example, U.S. Pat. No. 2,438,838 describes reacting a phenolic compound with hydrogen sulfide in the presence or absence of a dehydration catalyst at a superatmospheric pressure. Other methods are described in U.S. Pat. No. 2,490,257, directed to the vapor phase reaction of chlorobenzene and hydrogen sulfide in the presence of wood charcoal, and U.S. Pat. No. 3,799,989, directed to a non-catalytic process for preparing thiophenols from the same reactants.
Processes for preparing phenolic compounds have also been the subject of prior investigations. Thus, U.S. Pat. No. 2,862,035 discloses the treatment of ethers with an alkali metal and with molecular hydrogen to yield compounds containing hydroxyl groups and hydrocarbons, while German Patentschrift No. 730236 describes the cleavage of diphenylether in the presence of thorium oxide to provide phenol.
Methods involving the cleavage of certain diphenylethers to provide reaction products other than phenols have also been previously described. Thus, British Pat. No. 994,506 teaches the reaction of a phenol ether which contains at least one hydrogen atom in an ortho or para position to the --OH or ether group, with a sulfur chloride and hydrogen sulfide at a temperature in the range of from -50.degree. C. to +200.degree. C., recovering the polysulfide formed and reducing the polysulfide to the mercaptan.
However, all the prior art processes are subject to disadvantages in that they require costly catalytic or multi-step methods, or result in liberation of chlorine or hydrochloric acid, thus presenting pollution and environmental problems.